Internal combustion engine having combustion heater

ABSTRACT

An internal combustion engine having a combustion heater is constructed to prevent a thermal damage to the structure of an intake system due to combustion heat emitted from the combustion heater. The engine includes the combustion heater operating at a cold time. Cooling water is warmed by heat of combustion gas emitted from the combustion heater when in combustion, thereby speeding up a warm-up of the engine and enhancing a performance of a car room heater of a vehicle mounted with the engine. In the thus constructed internal combustion engine having the combustion heater, fresh air entering an intake air passageway of the engine is mixed with the combustion gas of the combustion heater, whereby the fresh air becomes a combustion gas mixed intake air toward an engine body. A temperature of the combustion gas mixed intake air is  − obtained, and a combustion state of the combustion heater is controlled based on this temperature.

This is a division of application Ser. No. 09/789,741 filed Feb. 22,2001, which is a division of application Ser. No. 09/204,8,95 filed Dec.3, 1998, U.S. Pat. No. 6,273,073.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an internal combustion engine having acombustion heater.

2.Related Background Art

It is required that a warm-up of an internal combustion engine bespeeded up at a cold time, and it is desirable to enhance a performanceof a car room heater of a vehicle mounted with the internal combustionengine.

This being the case, for example, Japanese Patent Application Laid-OpenPublication No. 62-75069 discloses a technology of increasing atemperature of the so-called engine cooling water contained in aninternal combustion engine body by utilizing combustion heat emittedfrom a combustion heater provided in a intake system separately from aninternal combustion engine body and thereby speeding up the warm-upthereof and enhancing the performance of the car room heater.

Such an effect can be expected on one hand, however, in the internalcombustion engine having the combustion heater, there might arise aserious concern about a thermal damage to a intake system structure onthe other hand because of an excessive rise in a intake systemtemperature due to an influence by combustion heat emitted from thecombustion heater.

SUMMARY OF THE INVENTION

It is a primary object of the present invention, which was devised undersuch circumstances, to provide a technology of preventing a thermaldamage to a intake system structure due to combustion heat emitted froma combustion heater in an internal combustion engine having a combustionheater.

To accomplish the above object, according to a first aspect of thepresent invention, an internal combustion engine having a combustionheater may comprise a combustion heater operating when the internalcombustion engine is in a predetermined operation state, and enginerelated elements warmed by heat of a combustion gas emitted by thecombustion heater during a combustion to speed up a warm-up of theinternal combustion engine and to enhance a performance of a car roomheater of a vehicle mounted with the internal combustion engine, whereinfresh air becomes a combustion gas mixed intake air flowing toward theinternal combustion engine body by mixing the combustion gas of thecombustion heater with the fresh air entering a intake air passageway ofthe internal combustion engine, a temperature of the combustion gasmixed intake air is obtained, and a combustion state of the combustionheater is controlled based on this temperature.

“When the internal combustion engine is in the predetermined operationstate” expressed herein may include a time when the engine is on theoperation or after starting up the internal combustion engine at a coldtime or at an extremely cold time, and when an heating value from theinternal combustion engine itself is small due to e.g., a burned fuelquantity is small as well as when a heat receiving value of coolingwater is thereby small. Then, the cold time implies that an outside airtemperature is approximately −10° C. to 15° C., and the extremely coldtime implies that the outside air temperature is lower thanapproximately −10° C.

The “engine related elements” may be engine cooling water and theinternal combustion engine itself in which the combustion gas of thecombustion heater is mixed in the intake air.

In the internal combustion engine having the combustion heater accordingto the present invention, the combustion gas emitted from the combustionheater operating when the internal combustion engine is in thepredetermined operation state, is mixed in the intake air passageway ofthe internal combustion engine, whereby fresh air having flowed so farthrough the intake air passageway becomes a high-temperature combustiongas mixed intake air assuming combustion heat of the combustion gas.

Then, before the combustion gas mixed intake air enters the internalcombustion engine body, a temperature of the combustion gas mixed intakeair is obtained, and a combustion state of the combustion heater iscontrolled based on the thus obtained temperature, precisely on a valueindicated by this temperature. Therefore, if this control is preferablycarried out, an excessive rise in the intake system temperature due tothe combustion heat can be restrained while speeding up the warm-up andenhancing the performance of the car room heater by utilizing thecombustion heat of the combustion heater. It is therefore feasible toprevent the thermal damage to the intake system structure.

“The control of the combustion state of the combustion heater” expressedherein is to control factors, such as a force and a magnitude etc. offlames in the combustion heater, for determining the increase anddecrease in the temperature of the combustion gas emitted from thecombustion heater.

What can be exemplified as the “factor” may be, for instance, quantitiesof the air and the fuel supplied for combustion to the combustion heateretc. Particularly in the case of a combustion heater structured toincrease a temperature of the engine cooling water by internallycirculating the engine cooling water, what can be exemplified as the“factor” may be, for instance a flow rate etc. of the engine coolingwater. By controlling those factors, if the combustion quantity of thecombustion heater augments, the flames gains a force to increase inmagnitude with the result that the temperature of the flames rises.Then, the temperature of the combustion gas emitted from the combustionheater also rises. Consequently, the temperature of the combustion gasmixed intake air also rises.

Whereas if the combustion quantity of the combustion heater decreases,the flames loses the force to decrease in magnitude, and the temperatureof the flames also loses, with the result that the temperature of thecombustion gas emitted from the combustion heater lowers. Consequently,the temperature of the combustion gas mixed intake air also lowers.

Moreover, the warm-up is speeded up by utilizing the combustion gas ofthe combustion heater, which emits almost no smokes, in other words,contains no carbon, and therefore it can be expected that the durabilitybe more enhanced than by a prior art EGR etc.

Then, since the combustion gas discharge passageway of the combustionheater communicates with the intake air passageway, the combustion gasof the combustion heater is again burned in the internal combustionengine. Subsequently, when the combustion gas can be, upon reaching theexhaust system of the internal combustion engine, purified by an exhaustcatalyst normally provide in this exhaust system.

Moreover, apertures of the combustion gas discharge passageway and theair supply passageway of the combustion heater are not exposed directlyto the atmospheric air, and hence an effect of reducing noises can beexpected.

According to a second aspect of the present invention, an internalcombustion engine having a combustion heater may further comprise acombustion gas mixed intake air temperature detecting element forobtaining a temperature of the combustion gas mixed intake air byactually measuring this temperature.

As “the combustion gas mixed intake air temperature detecting element”,e.g., a temperature sensor may be exemplified.

According to a third aspect of the present invention, an internalcombustion engine having a combustion heater may further comprise acombustion gas mixed intake air temperature calculating element forobtaining a temperature of the combustion gas mixed intake air bycalculating a temperature of the fresh air and a temperature of thecombustion gas. As a combustion gas mixed intake air temperaturecalculating element, it is preferable to use, for example, atwo-dimensional map consisting of a temperature of the fresh air beforebeing mixed with the combustion gas and an exhaust temperature of thecombustion gas.

“The two-dimensional map” is structured such that, for instance, theaxis of ordinates indicates the exhaust temperature of the combustiongas while the axis of abscissa indicates the temperature of the freshair before being mixed with the combustion gas, and a cross pointtherebetween indicates a temperature of the combustion gas mixed intakeair. Further, for obtaining the combustion gas mixed intake airtemperature corresponding to the rotational speed of the internalcombustion engine, it is desirable that there be prepared a plurality oftwo-dimensional maps corresponding to the rotational speed such as,e.g., 1000 rpm, 2000 rpm, . . . A read-only memory ROM incorporated intoan engine electronic control unit ECU is previously stored with theabove two-dimensional maps.

In the case of a combustion heater structured to increase a temperatureof the engine cooling water by internally circulating the engine coolingwater according to a fourth aspect of the present invention, in aninternal combustion engine having a combustion heater, the calculationby the combustion gas mixed intake air temperature calculating elementmay, when executing a calculation, include the rotational speed of theinternal combustion engine. In this case, the read-only memory ROM ispreviously stored with a specific arithmetic formula instead of thetwo-dimensional maps as a combustion gas mixed intake air calculatingelement.

For example, the following equation may be preferable as a “specificarithmetic formula”.

Tm={(1−α)T 1+kαT 2}/(1−α+kα)

where Tm: the calculated temperature of the combustion gas

mixed intake air,

T1: the temperature of the fresh air before being mixed with thecombustion gas,

T2: the exhaust temperature of the combustion gas,

Ne: the rotational speed

α: the quantity of the fresh air for combustion of combustion heater(the quantity is obtained by arithmetic formula: α=α0/Ne, where α0 isthe compensation constant when the rotational speed Ne differs and ispreferably, e.g., 0.2.), and

k: the compensation constant (when the fresh air α is supplied for thecombustion upon an operation of the combustion heater, a combustion gasα′ having a mass over the fresh air quantity α is emitted from thecombustion heater with burning of the fuel for combustion in thecombustion heater. The constant k is a numerical value determined takinginto consideration an existence of this combustion gas α′.)

Note that a combustion gas mixed intake air temperature calculatingelement may be constructed of a combination of the two-dimensional mapswith the arithmetic formula.

Further, the calculated temperature Tm of the combustion gas mixedintake air is the value taking the rotational speed (intake airquantity) into consideration, and may therefore be said to be highlyaccurate corresponding to the operation state of the internal combustionengine at the time concerned.

According to a fifth aspect of the present invention, an internalcombustion engine having a combustion heater, may comprise a combustionheater operating when the internal combustion engine is in apredetermined operation state, and engine related elements warmed byheat of a combustion gas emitted by the combustion heater during acombustion to speed up a warm-up of the internal combustion engine andto enhance a performance of a car room heater of a vehicle mounted withthe internal combustion engine, wherein a combustion state of thecombustion heater is controlled based on a temperature of fresh airitself entering an intake air passageway of the internal combustionengine.

The time “when the internal combustion engine is in the predeterminedoperation state” and “the engine related elements” expressed herein arethe same as those stated according to the first aspect of the invention.

In this case, an intake air temperature can be optimally controlledbecause of taking into consideration the temperature of the fresh airitself, i.e., the temperature of the intake air before being mixed withthe combustion gas.

According to a sixth aspect of the present invention, an internalcombustion engine having a combustion heater, may comprise a combustionheater operating when the internal combustion engine is in apredetermined operation state, and engine related elements warmed byheat of a combustion gas emitted by the combustion heater during acombustion to speed up a warm-up of the internal combustion engine andto enhance a performance of a car room heater of a vehicle mounted withthe internal combustion engine, wherein a combustion state of thecombustion heater is controlled based on a temperature of the combustiongas itself emitted from the combustion heater. The time “when theinternal combustion engine is in the predetermined operation state” and“the engine related elements” expressed herein are the same as thosestated according to the first aspect of the invention.

In this case, since the temperature of the combustion gas itself istaken into consideration, the intake air temperature can be optimallycontrolled.

According to a seventh aspect of the present invention, it is desirablethat a combustion quantity of the combustion heater be decreased whenthe temperature of the combustion gas mixed intake air flowing throughthe intake air passageway of the internal combustion engine, or thetemperature itself of the fresh air, or the temperature itself of thecombustion gas of the combustion heater is over a predetermined value.

“The predetermined value” given herein is a temperature enough to causethe thermal damage to the intake system structure.

In this case, considering the temperature enough to cause the thermaldamage to the intake system structure, the combustion quantity of thecombustion heater is decreased when the temperature of the combustiongas mixed intake air, or the temperature itself of the fresh air, or thetemperature of the combustion gas of the combustion heater is high, andit is therefore feasible to restrain a decline of the durability of theintake system.

According to an eighth aspect of the present invention, an internalcombustion engine having a combustion heater may comprise a combustionheater operating when the internal combustion engine is in apredetermined operation state, and engine related elements warmed byheat of a combustion gas emitted by the combustion heater during acombustion to speed up a warm-up of the internal combustion engine andto enhance a performance of a car room heater of a vehicle mounted withthe internal combustion engine. The combustion heater includes an airpassageway for supplying the air used for the combustion of the heatervia an intake air passageway of the internal combustion engine, and acombustion gas discharge passageway for discharging the combustion gasemitted from the combustion heater into the intake air passageway. Anair flow meter is provided at a portion, disposed upstream of aconnecting point between the combustion gas discharge passageway and theintake air passageway, of the intake air passageway.

The time “when the internal combustion engine is in the predeterminedoperation state” and “the engine related elements” expressed herein arethe same as those stated according to the first aspect of the invention.The combustion heater is connected in bypass to the intake airpassageway through the air supply passageway and the combustion gasdischarge passageway.

Further, the air flow meter may be defined as an air resisting structurewhich hinders a flow of air flowing through the intake air passageway,and therefore a pressure of the air flowing out of the air flow meter issmaller than a pressure of the air entering the air flow meter. Namely,the air flow meter has a difference in the air pressure between an inletand an outlet thereof.

Then, in this instance, since the air flow meter is provided at theportion disposed upstream of a connecting point between the combustiongas discharge passageway and the intake air passageway, thehigh-temperature exhaust gas of the combustion heater is not sucked inthe air flow meter. Hence, the thermal damage to the air flow meter canbe prevented.

According to a ninth aspect of the present invention, the air flow metermay also be provided between a connecting point of the intake airpassageway to the air supply passageway and a connecting point of theintake air passageway to the combustion gas discharge passageway.

In this case however, as for a type of the air flow meter, it isrequired that, for example, a hot wire type or film type air flow meterwith a less pressure difference between the inlet side and the outletside be used. With this contrivance, even when the air flow meter as theair resisting structure is provided between the connecting point of theintake air passageway to the air supply passageway and the connectingpoint of the intake air passageway to the combustion gas dischargepassageway, due to the existence of the air flow meter, it never happensthat an ignition becomes hard to attain because of an air flow velocitynot increasing inside the combustion heater.

According to a tenth aspect of the present invention, the air flow metermay be provided at a portion, disposed upstream of the connecting pointbetween the air supply passageway and the intake air passageway, of theintake air passageway.

In this instance, as for the type of the air flow meter, there may beused an air flow meter with a pressure difference between the inlet sideand the outlet side. The reason why so is that since there is providedno air flow meter along the intake air passageway between the connectingpoint of the air supply passageway to the intake air passageway and theconnecting point of the combustion gas discharge passageway to theintake air passageway, with respect to the combustion heater connectedin bypass to the intake air passageway, there is almost no pressuredifference between the connecting point, serving as an inlet of thebypass, of the air supply passageway to the intake air passageway andthe connecting point, serving as an outlet of the bypass, of thecombustion gas discharge passageway to the intake air passageway, andtherefore the air flow velocity becomes lower inside the combustionheater located between the air supply passageway and the combustion gasdischarge passageway that form the bypass, and also constituting a partof the bypass in communication therewith. Accordingly, awell-conditioned ignition of the combustion heater is attained at alltimes.

According to an eleventh aspect of the present invention, an internalcombustion engine having a combustion heater may comprise a combustionheater operating when the internal combustion engine is in apredetermined operation state, and engine related elements warmed byheat of a combustion gas emitted by the combustion heater during acombustion to speed up a warm-up of the internal combustion engine andto enhance a performance of a car room heater of a vehicle mounted withthe internal combustion engine, wherein the intake air passageway isprovided with a supercharger for pressurizing the intake air by forciblyintruding the intake air into the internal combustion engine body, and acombustion state of the combustion heater is controlled based on apressure of the intake air in the intake air passageway when thesupercharger is operated.

The time “when the internal combustion engine is in the predeterminedoperation state” and “the engine related elements” expressed herein arethe same as those stated according to the first aspect of the invention.

What can be exemplified as the “supercharger” may be a supercharger ofwhich a driving source is a rotational force of an output shaft of theinternal combustion engine, and a turbo charger, using an exhaustturbine, of which a driving force is a rotational force thereof.

According to a twelfth aspect of the present invention, a combustionquantity of the combustion heater may be decreased when the intake airpressure is equal to or higher than a set value. The “set value” givenherein is a value of a intake air pressure capable of exerting no.burden upon an inter cooler normally set coupled with the superchargeras well as being a certain fixed intake air pressure value set forpreventing an excessive rise in the intake air temperature due to anincrease in the intake air pressure.

With this contrivance, even when the temperature of the intake air riseswith the increased intake air pressure, the combustion quantity of thecombustion heater is reduced corresponding thereto, and a preferableintake air temperature can be thereby gained. It is therefore possibleto relieve the burden upon the inter cooler.

According to a thirteenth aspect of the present invention, thecombustion quantity of the combustion heater may be decreased when thetemperature of the combustion gas mixed intake air and the intake airpressure are respectively equal to or higher than specified values. Inthis case also, the burden on the inter cooler can be relieved. Notethat the specified value given herein is the same as the predeterminedvalue in the seventh aspect of the invention in the case of thetemperature of the combustion gas mixed intake air, and the set valuedescribed above in the case of the intake air pressure.

According to a fourteenth aspect of the present invention, an internalcombustion engine having a combustion heater may comprise a combustionheater, and engine related elements warmed by heat of a combustion gasemitted by the combustion heater during a combustion to speed up awarm-up of the internal combustion engine and to enhance a performanceof a car room heater of a vehicle mounted with the internal combustionengine, wherein the combustion gas of the combustion heater isintroduced into the intake air passageway of the internal combustionengine, and a combustion quantity of the combustion heater is decreasedwhen the internal combustion engine is in a predetermined operationstate with a small intake air quantity.

“The engine related elements” expressed herein are the same as thatstated according to the first aspect of the invention.

“The small intake air quantity” implies a case where the number ofengine rotations is small, and a case where an aperture of a throttlevalve is small, which are respectively explained in the followingfifteenth and sixteenth aspects of the invention.

When the combustion gas of the combustion heater enters the intake airpassageway, the fresh air becomes the combustion gas mixed intake airtoward the internal combustion engine. The combustion gas mixed intakeair is a mixed gas of the high-temperature combustion gas with the coldoutside fresh air. Hence, if the quantity of the combustion gascontained in the combustion gas mixed intake air per unit capacityremains the same, and if a quantity of the fresh air is small, thetemperature of the combustion gas mixed intake air rises. By contrast,if the quantity of the fresh air is large, the temperature of thecombustion gas mixed intake air lowers.

In the internal combustion engine having the combustion heater accordingto the present invention, when the internal combustion engine is in thepredetermined operation state with the small quantity of the air suckedinside the engine, i.e., with the small fresh air quantity, thecombustion gas quantity in the combustion heater is decreased, andconsequently the temperature of the combustion gas mixed intake airlowers. Accordingly, it is feasible to prevent the thermal damage frombeing exerted upon the intake system structure by controlling well theratio of the combustion gas to the fresh air.

According to a fifteenth aspect of the present invention, the rotationalspeed may be set under a predetermined value when in the predeterminedoperation state.

“When in the predetermined operation state” expressed herein is the sameas that stated in the fourteenth aspect of the invention.

“The predetermined value of the rotational speed” is a specifiedrotational speed set slightly higher than another specified rotationalspeed. The former specified rotational speed is hereinafter referred toas a target rotational speed. The latter is hereinafter referred to as alimit rotational speed. The limit rotational speed is a rotational speedfor ensuring an intake air quantity making the combustion gas mixedintake air temperature high enough to exert the thermal damage to thestructure of intake system if the internal combustion engine is drivenwith this limit rotational speed, and if the combustion heater continuesto operate with the driving of the internal combustion engine.

The reason why the target rotational speed is set higher than the limitrotational speed, is that an allowance of some extent is given to therotational speed because it might be a trouble that the thermal damageis exerted on the structure of intake system upon reaching of therotational speed to the target rotational speed.

According to a sixteenth aspect of the present invention, an aperture ofa throttle valve may be set under a predetermined value when in thepredetermined operation state.

“When in the predetermined operation state” expressed herein is the sameas that stated in the fourteenth aspect of the invention.

“The predetermine value of the throttle valve aperture” given herein isa numerical value for indicating a target throttle valve aperture setsomewhat higher than a limit throttle valve aperture. The limit throttlevalve aperture is a certain throttle valve aperture for ensuring anintake air quantity making the combustion gas mixed intake airtemperature high enough to exert the thermal damage to the structure ofintake system if the internal combustion engine is driven with thislimit throttle aperture when the throttle valve is opened, and if thecombustion heater continues to operate in this driven state.

The reason why the target throttle valve aperture is set higher than thelimit throttle valve aperture, is that an allowance of some extent isgiven to the throttle valve aperture because it might be a trouble thatthe thermal damage is exerted on the structure of intake system uponreaching of the throttle valve aperture to the target throttle valveaperture.

According to a seventeenth aspect of the present invention, thecombustion heater may be stopped when in the predetermined operationstate.

“When in the predetermined operation state” expressed herein is the sameas that stated in the fourteenth aspect of the invention.

“The combustion heater is stopped” may imply, for example, a halt of afuel pump for supplying fuels to combustion cylinders in which toproduce flames serving as a combustion source of the combustion heater,and a halt of a blowing fan, or a combination thereof.

In the internal combustion engine having the combustion heater of thepresent invention, the combustion heater stops when in the predeterminedoperation state, i.e., when the quantity of the air sucked inside by theinternal combustion engine is small. Then, if the combustion heaterstops with a halt of the fuel pump, the fuel supply is cut off, and itfollows that the flames are produced by only the residual fuel in thecombustion heater. Normally, the residual quantity is small, andconsequently a duration of flaming comes to an end in a short time.Hence, a heating value of the combustion heater is remarkably reduced.As a result, the thermal damage to the intake system structure can beprevented when the engine intake quantity is small.

Furthermore, when the combustion heater stops with the halt of theblowing fan, even if the flames leaks out of the combustion heater, itis impossible to supply the air warmed by the flames toward the interiorof the internal combustion engine spaced away from the combustion heaterbecause of the blowing fan having stopped, and it follows that thecombustion heater substantially does not operate.

Moreover, in the case of the combination type in which the combustionheater stops with the halt of the fuel pump and the halt of the blowingfan, it follows that the combustion heater does not operate completely.

According to an eighteenth aspect of the present invention, an internalcombustion engine having a combustion heater may comprise a combustionheater, and engine related elements warmed by heat of a combustion gasemitted by the combustion heater during a combustion to speed up awarm-up of the internal combustion engine and to enhance a performanceof a car room heater of a vehicle mounted with the internal combustionengine, wherein the combustion heater operates during not only anoperation but also a halt of the internal combustion engine, acombustion gas of the combustion heater is introduced into a body of theinternal combustion engine during the operation of the internalcombustion engine, and the combustion gas of the combustion heater isintroduced into an exhaust system of the internal combustion engineduring the halt of the internal combustion engine.

“The operation of the internal combustion engine” expressed hereinimplies a state where a piston reciprocates within the cylinder, and“the stop of the internal combustion engine” implies a state where thepiston does not reciprocate within the cylinder and remains stopped.Then, the combustion heater according to the present invention iscontrived to operate solely independently if a proper operation switchfor operating the combustion heater is turned ON even when the internalcombustion engine is in the stopped state.

In the internal combustion engine having the combustion heater accordingto the present invention, during the operation of the internalcombustion engine, the combustion gas of the combustion heater isintroduced into the body of the internal combustion engine and thereforere-burned in the cylinders of the internal combustion engine while beingsupplied for speeding up the warm-up. Since the re-burned combustion gasof the combustion heater emits almost no smokes, in other words,contains no carbon, an enhancement of the durability of the internalcombustion engine can be expected.

Further, if the combustion heater operates during the halt of theinternal combustion engine, the combustion gas emitted out of thecombustion heater is flowed to the exhaust system of the internalcombustion engine and discharged therefrom into the atmospheric air,which may be said to be sufficiently satisfactory as a measure againstthe exhaust gas of the combustion heater. Accordingly, since thetreatment of the exhaust gas of the combustion heater is sufficient evenduring the stop of the internal combustion engine, it never happens thatthe combustion heater stops due to an insufficient treatment of theexhaust gas of the combustion heater, and the combustion heater can beindependently operated. The combustion heat of the combustion heater isnormally also utilized for warming the air blown from the car roomheater. Therefore, if the combustion heater is made to work beforegetting in the car, the car room heater can be switched ON beforehand,so that the interior of the car room is warm and comfortable even at thecold time. Note that a process of previously switching ON and warming upthe combustion heater may be termed pre-heating of the combustionheater.

Then, when the combustion heater is in a pre-heating state, thecombustion gas emitted from the combustion heater is introduced into theexhaust system, and therefore, on the occasion of this introduction,there may be prepared an element for preventing the combustion gas frompassing through the intake system of the internal combustion engine, andan element for sufficiently decreasing the temperature of the combustiongas so that the intake system, even when passing through the intakesystem, does not suffer from the thermal damage by the combustion gas.What can be exemplified as the element for decreasing the temperature ofthe combustion gas may be, e.g., an exhaust cooler. It is preferablethat the exhaust cooler be disposed, e.g., in the combustion gasdischarge passageway through which to connect the combustion heater tothe intake system of the internal combustion engine.

According to a nineteenth aspect of the present invention, it ispreferable that the combustion gas be discharged into the exhaust systemby opening an exhaust gas re-circulation passageway constituting an EGRsystem.

“The EGR system” described herein is a system for returning a part ofthe exhaust gas to the intake system and introducing the exhaust gasagain into the cylinders. “The exhaust gas re-circulation passageway” isa principal component of the EGR system and is a passageway forre-circulating the exhaust gas from the exhaust air passageway of theinternal combustion engine to the intake air passageway thereof, whichare connected in bypass to the cylinders of the internal combustionengine. Further, the exhaust gas re-circulation passageway has an EGRvalve for controlling a flow rate of the re-circulated exhaust gas.

In the internal combustion engine having the combustion heater accordingto the present invention, in the case of a vehicle provided with the EGRsystem, the combustion gas of the combustion heater can be discharged tothe exhaust system by using the exhaust gas re-circulation passageway,it is therefore possible to reduce the costs as well as providing thesufficient measure against the exhaust gas of the combustion heater evenduring the halt of the internal combustion engine.

These together with other objects and advantages which will besubsequently apparent, reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will becomeapparent during the following discussion in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic diagram showing a first embodiment of an internalcombustion engine having a combustion heater according to the presentinvention;

FIG. 2 is a sectional view schematically illustrating the combustionheater;

FIG. 3 is a flowchart showing an operation control routine in the firstembodiment in FIG. 1;

FIG. 4 is a chart showing a combustion gas mixed intake air temperatureprediction map;

FIG. 5 is a schematic diagram showing a second embodiment of theinternal combustion engine having the combustion heater according to thepresent invention;

FIG. 6 is a flowchart showing an operation control routine in the secondembodiment in FIG . 5;

FIG. 7 is a schematic diagram showing a third embodiment of the internalcombustion engine having the combustion heater according to the presentinvention;

FIG. 8 is a schematic diagram showing a fourth embodiment of theinternal combustion engine having the combustion heater according to thepresent invention;

FIG. 9 is a schematic diagram showing a fifth embodiment of the internalcombustion engine having the combustion heater according to the presentinvention;

FIG. 10 is a flowchart showing an operation control routine in the fifthembodiment in FIG. 9;

FIG. 11 is a schematic diagram showing a sixth embodiment of theinternal combustion engine having the combustion heater according to thepresent invention;

FIG. 12 is a flowchart showing an operation control routine in the sixthembodiment in FIG. 11;

FIG. 13 is a schematic diagram showing a seventh. embodiment of theinternal combustion engine having the combustion heater according to thepresent invention;

FIG. 14 is a flowchart showing an operation control routine in theseventh embodiment in FIG. 13;

FIG. 15 is a schematic diagram showing an eight embodiment of theinternal combustion engine having the combustion heater according to thepresent invention;

FIG. 16 is a flowchart showing an operation control routine in theeighth embodiment in FIG. 15;

FIG. 17 is a schematic diagram showing a ninth embodiment of theinternal combustion engine having the combustion heater according to thepresent invention; and

FIG. 18 is a flowchart showing an operation control routine in the ninthembodiment in FIG. 17.

DETAILED DESCRIPTION

Embodiments of the present invention will hereinafter be described withreference to the accompanying drawings.

<First Embodiment>

A first embodiment of the present invention will hereinafter bediscussed with reference to FIGS. 1 to 4.

An engine 1 classified as an internal combustion engine is of a watercooling type, and includes an engine body 3 having an unillustratedwater jacket through which cooling water is circulated, a air intakedevice 5 for supplying a plurality of cylinders (not shown) of theengine body 3 with air needed for combustion, an exhaust device 7 fordischarging, into the atmospheric air, an exhaust gas after a fuel-airmixture has been burned in the cylinders, and a car room heater 9 forwarming a car interior of a vehicle mounted with the engine 1.

The air intake device 5 originates with an air cleaner 13 which is fortaking fresh air into the cylinders. Then, a compressor 15a of a turbocharger 15, a combustion heater 17, an inter-cooler 19 and a intakemanifold 21, are provided as intake system structures between the aircleaner 13 and an unillustrated intake port of the engine body 3 definedas the terminal of the air intake device 5.

These intake system structures belongs to a intake pipe including aplurality of connection pipes.

The intake pipe 23 is divided roughly by the compressor 15 a into twoparts, an upstream-side connection pipe 25 and a downstream-sideconnection pipe 27. The downstream-side connection pipe 27, into whichthe outside air flowing in the intake device 5 is forcibly intruded bythe compressor 15 a. Thus the pipe 27 is brought into a pressurizedstate. And an upstream-side connection pipe 25 is not brought into thepressurized state.

Referring to FIG. 1, the upstream-side connection pipe 25 is constructedof a main pipe 29 taking a rod-like shape extending straight toward thecompressor 15 a from the air cleaner 13, and a heater branch pipe 31serving as a tributary pipe connected in bypass to the main pipe 29.

An outside air temperature sensor 32 is fitted to a portion, vicinal tothe down-stream-side of the air cleaner 13, of the main pipe 29. Outsideair al flowing in the main pipe 29 from the air cleaner 13 is fresh airagainst the exhaust gas of the engine 1, and a temperature thereof isdetected by the outside air temperature sensor 32.

The heater branch pipe 31 embraces the combustion heater 17 midwaysthereof, and connects to the main pipe 29 an upstream-side portion ofthe combustion heater 17 in an air flowing direction. The heater branchpipe 31 includes an air supply passageway 33 for supplying the air,i.e., the fresh air to the combustion heater 17 via the main pipe 29.The heater branch pipe 31 further includes a combustion gas dischargepassageway 35, through which to connect the downstream-side portion ofthe combustion heater 17 in the air flowing direction to the main pipe29, for discharging the burned (exhaust) gas coming from the combustionheater 17 into the main pipe 29. Note that the air relative to theheater branch pipe 31 implies not only the fresh air al but also acombustion gas a2 emitted from the combustion heater. The combustion gasof the combustion heater is a gas emitting almost no smokes, in otherwords, a gas containing no carbon. Hence the above combustion gas has noproblem when used as the intake air of the internal combustion engine.

A combustion gas temperature sensor 36 is attached to a portion, closerto the combustion heater 17, of the combustion gas discharge passageway35. The temperature sensor 36 detects a temperature of the combustiongas of the combustion heater 17 before entering the main pipe 29 fromthe combustion heater 17.

Connecting points c1, c2 are respectively of the air supply passageway33 to the main pipe 29 and of the combustion gas discharge passageway 35to the main pipe 29, the connecting point c1 is located more upstream ofthe main pipe 29 than the connecting point c2. Hence, the air a1 fromthe air cleaner 13 is separated into the air a1 diverging at first tothe heater branch pipe 31 at the connecting point c1, and air a1′ notdiverging but flowing via the main pipe 29 toward the connecting pointc2. Air a2 turned to be a combustion gas from the diverging air a1 afterbeing burned in the combustion heater 17 and the fresh air a1′ notdiverging at the connecting point c1, become confluent at the connectingpoint c2 and become combustion gas mixed air a3.

The air a1 diverging at the connecting point c1 flows via such as theair supply passageway 33→the combustion heater 17→ the combustion gasdischarge passageway 35, and, after becoming the air a2, returns to themain pipe 29 from the connecting point c2. The air a2 returned to themain pipe 29 is the combustion gas having been burned and assuming theheat in the combustion heater 17 and therefore, when confluent with thenon-diverging air a1′ at the connecting point c2, becomes the combustiongas mixed air a3. Then, as a result, this combustion gas mixed air a3turns out to be high-temperature intake air entering the engine body 3.A combustion state of the combustion heater 17 is controlled bypredicting a temperature of the combustion gas mixed intake air a3. Thiscontrol method will be discussed later on.

Referring again to FIG. 1, the downstream-side connecting pipe 27connects the compressor 15 a to the intake manifold 21, and takes asubstantially L-shape as far as the pipe 27 shown in FIG. 1 isconcerned.

Further, the inter-cooler 19 is disposed in a portion closer to theintake manifold 21.

On the other hand, the exhaust device 7 originates from an unillustratedexhaust port of the engine body 3 and terminates with a silencer 41, inwhich section there are provided an exhaust manifold 37, a turbine 15 bof the turbo charger 15 and an exhaust catalyst 39 along an exhaust pipe42. These well-known components are not directly related to the presentinvention, and hence the explanation thereof is omitted herein. The airflowing through the exhaust device 7 is designated by a reference symbola4 as an exhaust gas of the engine 1.

Next, FIG. 2 schematically illustrates a structure of the combustionheater 17.

The combustion heater 17 is linked to the water jacket of the enginebody 3 and includes inside a cooling water passageway 17 a through whichthe cooling water from the water jacket flows. The cooling water(indicated by a broken arrow-line) flowing via the cooling waterpassageway 17 a runs around a combustion chamber 17 d defined as acombustion unit formed inwardly of the combustion heater 17, duringwhich time the cooling water receives the heat from the combustionchamber 17 d and is thus warmed up. This process will be sequentiallyexplained in greater details.

The combustion chamber 17 d is constructed of a combustion cylinder 17 bserving as a combustion source from which emit a flame, and acylindrical partition wall 17 c for covering the combustion cylinder 17b and thus preventing the flame from spreading outside. The combustioncylinder 17 b is covered with the partition wall 17 c, whereby thecombustion chamber 17 d is defined inside by the partition wall 17 c.Then, this partition wall 17 c is also covered with an outer wall 43 aof the combustion heater 17, and there is a spacing therebetween. Withthis spacing, the cooling water passageway 17 a is formed between aninternal surface of the outer wall 43 a and an external surface of thepartition wall 17 c.

Further, the combustion chamber 17 d has an air supply port 17 d 1 andan exhaust gas discharge port 17 d 2, which are respectively connecteddirectly to the air supply passageway 33 and to the combustion gasdischarge passageway 35. The air al coming from the air supplypassageway 33 enters the combustion chamber 17 d via the air supply port17 d 1 and arrives, after flowing therethrough, at the exhaust gasdischarge port 17 d 2. Thereafter, as described above, the air a1 flowsas the air a2 into the main pipe 29 via the combustion gas dischargepassageway 35. Hence, the combustion chamber 17 d is formed as an airpassageway through which to flow the air a1 changed into the air a2 byits being burned in the combustion heater 17.

Then, the air a2, which is returned to the main pipe 29 via thecombustion gas discharge passageway 35 after being burned in thecombustion heater 17, is the so-called exhaust gas discharged from thecombustion heater 17 and therefore assumes the heat. Then, the air a2holding the heat is discharged from the combustion heater 17, duringwhich time the heat of the air a2 is transmitted via the partition wall17 c to the cooling water flowing inside the cooling water passageway 17a and, as explained above, warms up the cooling water. Therefore, thecombustion chamber 17 d serves also as a heat exchange passageway.

Note that the combustion cylinder 17 b includes a fuel supply pipe 17 econnected to an unillustrated fuel pump. A fuel for combustion is, uponreceiving a pump pressure of the fuel pump, supplied to the combustioncylinder 17 b from the fuel supply pipe 17 e. The supplied fuel forcombustion is vaporized within the combustion heater 17, therebybecoming a vaporized fuel. The vaporized fuel is ignited by anunillustrated ignition source.

It is to be noted that the air supply passageway 33 and the combustiongas discharge passageway 35 are used for only the combustion heater 17and may be therefore classified as members belonging to the combustionheater 17.

Next, a circulation of the cooling water will be explained.

The cooling water passageway 17 a has a cooling water intake port 17 a 1connected to the water jacket and a cooling water discharge port 17 a 2connected to the car room heater 9.

A water conduit W1 is provided between the cooling water intake port 17a 1 and the engine body 3, and a water conduit W2 is connected tobetween the cooling water discharge port 17 a 2 and the car room heater9.

The combustion heater 17 is connected through these water conduits W1,W2 to the water jacket of the engine body 3 and to the car room heater9. Further, the car room heater 9 is also connected via a water conduitW3 to the engine body 3.

Accordingly, the cooling water in the water jacket of the engine body 3flows, as a flowing sequence (1), to the combustion heater 17 from thecooling water intake port 17 a 1 via the water conduit W1, so that thecooling water is warmed up in the combustion heater 17. The warmed waterflows, as a flowing sequence (2), to the car room heater 9 from thecooling water discharge port 17 a 2 of the combustion heater 17 via thewater conduit W2. The water then returns, as a flowing sequence (3), tothe water jacket via the water conduit W3 after the water has beensubjected to the heat-exchange in the car room heater 9 with itstemperature decreased.

Thus, the cooling water is circulated between the engine body 3, thecombustion heater 17 and the car room heater 9 via the water conduitsW1, W2, W3.

Further, the combustion chamber body incorporates, in addition to theabove components, a blowing fan and a central processing unit (CPU) 47for controlling the combustion heater 17, which is separated from anengine electronic control unit (ECU) 46. The CPU 47 may not be, however,provided.

The ECU 46 is electrically connected via the CPU 47 to the outside airtemperature sensor 32, the combustion gas temperature sensor 36, arotational-speed sensor 59, the blowing fan 45 and the fuel pump. Notethat the ECU 46 is, if the CPU 47 is not provided, electricallyconnected directly to the combustion gas temperature sensor 36, thenumber-of-rotations sensor 59, the blowing fan 45 and the fuel pump.Then, the CPU 47 of the combustion heater 17 operates in accordance withparameters of the sensors 32, 36, 59, thereby controlling a combustionstate of the combustion heater 17. In other words, a force, a magnitudeand a temperature of the flame of the combustion heater 17 arecontrolled, and, with this control, a temperature of the exhaust gas(combustion gas) of the combustion heater 17 is controlled. Further, ifthe CPU 47 is not provided, the combustion state of the combustionheater 17 is directly controlled by the unillustrated CPU of the ECU 46.

Th e temperatures detected by the outside air temperature sensor 32 andthe combustion gas temperature sensor 36, are referred to as a fresh airtemperature and a combustion heater exhaust gas temperature respectivelybefore being mixed with the combustion gas, and are indicated by T1 andT2, respectively. A random access memory RAM of the ECU 46 istemporarily stored with the fresh air temperature T1 and the combustionheater exhaust gas temperature T2 before the mixing with the combustiongas, and as explained above these temperatures are appropriately invokedto the CPU 47 when predicting a temperature of the combustion gas mixedintake air. Furthermore, if the CPU 47 is not provided, thosetemperatures are invoked to an unillustrated CPU inside the ECU 46.

Then, an unillustrated read-only memory of the ECU 46 is stored with acombustion gas mixed intake air temperature prediction map M as shown inFIG. 4. The map M is prepared for predicting a temperature of the intakeair after being mixed with the combustion gas, and is created based on arelationship between the fresh air temperature T1 and the combustionheater exhaust gas temperature T2 after measuring a multiplicity oftemperatures of the intake air after being mixed with the combustiongas. Note that the temperature of the intake air after being mixed withthe combustion gas is hereinafter termed a combustion gas mixed intakeair temperature if not particularly notified.

Next, a method of predicting the combustion gas mixed intake airtemperature will be explained.

The map M is a “Combustion Heater Exhaust Gas Temperature—Intake AirTemperature Diagram”, wherein the axis of ordinates indicates thecombustion heater exhaust gas temperature T2, and the axis of abscissaindicates the intake air temperature T1. Cross points Tm1, Tm2, . . . ofa plurality of temperatures T2, T1, which are exemplified in thisdiagram, imply predicted temperatures of the combustion gas mixed intakeair temperature. Note that since there are the multiplicity of crosspoints Tm1, Tm2, . . . and hence these cross points are genericallycalled Tm. The map M implies that the cross points Tm are proportionalto T2 or/and T1.

Here, even if T2 with a given rotational speed takes the same value asT2 with a different rotational speed, and even if T1 with the givenrotational speed takes the same value as T1 with the differentrotational speed, it proves from the tests by the inventors that thepredicted temperature Tm becomes different when a rotational speed Nediffers. Accordingly, for obtaining the predicted temperature Tm suitedto the rotational speed Ne, there are prepared a plurality of thecombustion gas mixed intake air temperature maps M corresponding toevery rotational speed such as, e.g., 1000 rpm, 2000 rpm and so on.

Thus, the combustion gas mixed intake air temperature is predicted byutilizing the combustion gas mixed intake air temperature maps M, andhence the ECU 46 having the read-only memory ROM stored with the maps Mis called a mixed intake air temperature predicting unit.

Further, the predicted temperature Tm is obtained also by using anarithmetic formula instead of the maps M.

The following equation (1) is what is called herein the arithmeticformula.

Tm={(1−α)T 1+kαT 2}/(1−α+kα)  (1)

According to the equation (1), the fresh air temperature T1 before beingmixed with the combustion gas, the combustion heater exhaust gastemperature T2 and the rotational speed Ne are variables, and thepredicted temperature Tm of the combustion gas mixed intake air isobtained based on these variables.

In the above equation (1), however, a is the quantity of the fresh airdiverging from the main pipe 29 to the air supply passageway 33 andsupplied for the combustion by the combustion heater 17, and is givensuch as α=α0/Ne, where α0is the compensation constant when therotational speed differs and is preferably set to a numerical value onthe order of 0.2 in an empirical sense.

In the equation (1), k is the compensation constant determined byconsidering an existence of a combustion gas α′ because of the fact thatwhen the fresh air quantity a is supplied for the combustion upon anoperation of the combustion heater 17, the combustion gas α′ having amass greater than α′ due to a combustion of the combustion fuel isemitted out of the combustion heater 17.

When obtaining the predicted temperature Tm using the equation (1), theread-only memory ROM is stored with the equation (1) replacing the mapsM.

Hence, the ECU 46 may be defined as a combustion gas mixed intake airtemperature calculating unit including the arithmetic formula forcalculating the predicted temperature of the combustion gas mixed intakeair. Note that a concept of the calculation shall embrace the case ofusing the maps and the case of using the arithmetic formula.

What has been describes so far is the internal combustion engine 1having the combustion heater in accordance with the first embodiment.

Next, an operation control routine of an exhaust control device A1 ofthe internal combustion engine will be explained with reference to FIG.3.

This control routine is a part of a normal flowchart (not shown) whendriving the engine 1, and consists of steps 101-105 which willhereinafter be described. Further, all the operation in the followingprocedures are performed by the ECU 46. Note that the steps areabbreviated such as S101 in the case of, e.g., the step 101.

After starting the engine 1, the processing moves to this routine. InS101, it is judged whether or not the engine 1 is in an operation stateneeded for actuating the combustion heater 17. Note that the actuationof the combustion heater 17 implies switching ON the combustion heater17.

The time when the engine 1 is in the operation state needed forswitching ON the combustion heater 17 may include a time when the engineis on the operation or after starting up the engine 1 at a cold time orat an extremely cold time, and when a heating value from the engine body3 itself is small (e.g., a burned fuel quantity is small) as well aswhen a heat receiving value of the cooling water is thereby small. Then,the cold time implies that the outside air temperature is −10° C. to−15° C., and the extremely cold time implies that the outside airtemperature is lower than −10 C.

If judged to be affirmative in S101, the processing advances to nextS102. Whereas if judged to be negative, this routine is ended. Thenegative judgement may be, for instance, a case of having no necessityfor speeding up the warm-up of the internal combustion engine byoperating the combustion heater 17 or for warming the interior of thecar room of the vehicle mounted with the engine 1 by use of the car roomheater 9 because of the outside air temperature being high.

In S102, the predicted temperature Tm corresponding to the rotationalspeed Ne is obtained from the maps M schematically shown in FIG. 4 orfrom the equation (1).

After the predicted temperature Tm has been obtained in S102, theprocessing proceeds to S103.

It is judged in S103 whether or not the predicted temperature Tm is overa predetermined value. The predetermined value given herein is acombustion gas mixed intake air temperature enough to cause a thermaldamage to the structure of intake system.

If Tm≧the predetermined value, the judgement is affirmative, and theprocessing advances to S104. Whereas if not, the judgement is negative,and the processing proceeds to S105.

In S104, since it must be a trouble that the predicted combustion gasmixed intake air temperature is high enough to cause the thermal damageto the intake system structure, the output of the combustion heater 17is reduced down to a target value “1”. The target value “1” is definedas a specified set value so that the above temperature becomes such acombustion gas mixed intake air temperature as to cause no thermaldamage to the structure of intake system by, e.g., decreasing a pressureof the fuel pump relative to the fuel supply pipe 17 e for supplying thecombustion heater 17 with the fuel for combustion or by decreasing therotational speed of the blowing fan 45 under the control of the CPU 47or under the control of the ECU 46 if the CPU 47 is not provided inorder to reduce the output of the combustion heater 17.

The target value “1” given herein is an output value of the combustionheater 17, which is enough not to cause the thermal damage to thestructure of intake system due to the combustion gas mixed intake airtemperature in the case of using, when the outside air temperature ishighest enough to make the driver and persons riding together feel itnecessary to use the combustion heater 17, i.e., 15° C. at the coldtime, the outside air having this temperature as the air for combustionin the combustion heater 17.

In S105, the predicted combustion gas mixed intake air temperature isnot enough to cause the thermal damage to the structure of intakesystem, and therefore the output value of the combustion heater 17 isincreased up to a target value “2” higher than the target value “1” sothat the warm-up of the engine 1 is speeded up and a temperature of hotair coming from the car room heater 9 is increased as quickly aspossible.

Explained next are the operation and effect of the internal combustionengine A1 having the combustion heater in the first embodiment.

In the internal combustion engine A1 having the combustion heater, atthe cold time or extremely cold time, the combustion heater 17 operatesduring the operation of the engine 1 or after actuating the engine 1,and when the heating value from the engine body 3 itself is small (e.g.,when the burned fuel quantity is small) and when the heat receivingvalue of the cooling water is thereby small. The combustion gas a2emitted from the thus operated combustion heater 17 is mixed into themain pipe 29 of the intake passageway 23 of the engine 1, whereby thehigh-temperature combustion gas mixed intake air a3 assuming thecombustion heat of the combustion gas flows through the main pipe 29.

Then, before the combustion gas mixed intake air a3 enters the enginebody 3, the combustion gas mixed intake air temperature Tm is predicted,and the combustion state of the combustion heater 17 is controlled basedon the predicted temperature Tm, more precisely, the value indicated bythe temperature Tm. Hence, if this control is preferably carried out, itis feasible to restrain an excessive rise in the intake systemtemperature due to the combustion heat while speeding up the warm-up andenhancing the performance of the car room heater 9 by utilizing thecombustion heat of the combustion heater 17. It is therefore possible toprevent the thermal damage to the structure of intake system. Then, thecombustion gas mixed intake air temperature Tm is obtained by thecalculation considering the rotational speed (intake air quantity) andmay be therefore precise corresponding to the operation state of theengine 1 at the time concerned.

Further, the warm-up is speeded up by using the combustion gas a2 of thecombustion heater 17 which produces almost no smokes, in other words,contains no carbon, so that the durability of the engine 1 is, it can beexpected, also enhanced.

Moreover, since the combustion gas discharge passageway 35 of thecombustion heater 17 communicates with the main pipe 29, the combustiongas of the combustion heater 17, when reaching the discharge pipe 42after being burned in the engine 1, is purified by the exhaust catalyst39 normally provided in the exhaust pipe 42, and hence there is nonecessity for specially providing an equipment for purifying thecombustion gas of the combustion heater 17.

Furthermore, the apertures of the air supply passageway 33 and of thecombustion gas discharge passageway 35 of the combustion heater 17 arenot exposed directly to the atmospheric air, and therefore an effect ofreducing the noises can be expected.

<Second Embodiment>

A second embodiment of the present invention will hereinafter bediscussed with reference to FIGS. 5 and 6.

The internal combustion engine having the combustion heater in thesecond embodiment is designated by the reference symbol A2.

A difference of the internal combustion engine A2 having the combustionheater from the internal combustion engine A1 having the combustionheater in the first embodiment, is such a point that a intake airtemperature after being mixed with the combustion gas is not predictedbut actually measured, and the combustion state of the combustion heateris controlled based on this measured value. With this difference, theconstruction thereof is slightly different therefrom. Hence, theexplanation is concentrated upon only the different point, and the likecomponents are marked with the like reference symbols with an omissionof the explanation thereof.

The internal combustion engine A2 having the combustion heater includesneither the outside air temperature sensor 32 nor the combustion gastemperature sensor 36 of the internal combustion engine A1 having thecombustion heater in the first embodiment, but instead includes a mixedgas intake air temperature detection sensor 60 for detecting acombustion gas mixed intake air temperature, which is provided in aproper portion located in the vicinity and downstream of the connectingpoint c2 between the combustion gas discharge passageway 35 and the mainpipe 29. Another different point is that a value of the injectionquantity of the fuel injected into the cylinders of the engine body 3 isinputted as a piece of data to the ECU 46. Herein, the fuel injectionquantity is used as a substitute parameter for the intake air quantityin the first embodiment. Further, the intake air quantity is a valuedetermined by the rotational speed and an accelerator aperture.

Next, an operation control routine of an exhaust control device A2 ofthe internal combustion engine will be explained with reference to FIG.6. This control routine is also a part of a normal flowchart (not shown)when driving the engine 1, and consists of steps 201-205 which willhereinafter be described.

After starting the engine 1, the processing moves to this routine. InS201, it is judged whether or not the engine 1 is in the operation stateneeded for actuating the combustion heater 17.

The description about whether or not the engine 1 is in the operationstate needed for switching ON the combustion heater 17 is the same as inthe first embodiment. Note that this is the same with other embodimentswhich will be discussed later on.

If judged to be affirmative in S201, the processing advances to nextS202. Whereas if judged to be negative, this routine is ended. Thenegative judgement may be, for instance, a case of having no necessityfor speeding up the warm-up of the internal combustion engine byoperating the combustion heater 17 or for warming the interior of thecar room of the vehicle mounted with the engine 1 by use of the car roomheater 9 because of the outside air temperature being high.

In S202, a mixed intake air temperature Tm′ of the fresh air with thecombustion gas of the combustion heater 17 is obtained based on anactual measurement by use of the mixed gas intake air temperaturedetection sensor 60. This mixed gas intake air temperature Tm′ isinputted to the RAM of the ECU 46.

After obtaining the mixed gas intake air temperature Tm′ in S202, theprocessing advances to S203.

It is judged in S203 whether or not the mixed gas intake air temperatureTm′ is over a predetermined value. The predetermined value given hereinis a combustion gas mixed intake air temperature enough to cause thethermal damage to the structure of intake system.

If Tm′≧the predetermined value, the judgement is affirmative, and theprocessing advances to S204. Whereas if not, the judgement is negative,and the processing proceeds to S205.

Steps S204 and S205 corresponds to S104 and S105 in the firstembodiment, and hence the explanation thereof is omitted.

The internal combustion engine A2 having the combustion heater in thesecond embodiment exhibits the following operation and effect whileenhancing the performance of the car room heater and speeding up thewarm-up by utilizing the combustion heater of the combustion heater 17as in the case of the internal combustion engine A1 having thecombustion heater in the first embodiment.

To be specific, in the internal combustion engine A2 having thecombustion heater, there is actually measured the combustion gas mixedintake air temperature Tm′ after the combustion gas of the combustionheater 17 has been mixed with the fresh air, and the combustion state ofthe combustion heater 17 is controlled based on this measured value. Itis therefore feasible to restrain an excessive rise in the intake systemtemperature more precisely than in the predicted temperature Tm in theinternal combustion engine A1 having the combustion heater in the firstembodiment. Accordingly, the thermal damage to the structure of intakesystem is more effectively prevented. Note that if the accuracy of thepredicted temperature Tm is enhanced in the first embodiment, as amatter of course, the excessive rise in the intake system temperaturecan be restrained without any inferiority.

<Third Embodiment>

A third embodiment of the present invention will be described referringto FIG. 7.

The internal combustion engine having the combustion heater in the thirdembodiment is designated by the reference symbol A3. A difference of theinternal combustion engine A3 having the combustion heater from theinternal combustion engines A1, A2 each having the combustion heater inthe first and second embodiments, is only the point that an air flowmeter 70 is provided at a portion of the main pipe 29 between theconnecting points c1 and c2 of the air supply passageway 33 and thecombustion gas discharge passageway 35 to the main pipe 29, in otherwords, at a portion disposed upstream of the connecting point c2 of thecombustion gas discharge passageway 35 to the main pipe 29. Hence, thisconstruction can be applied to both of the internal combustion enginesA1, A2 having the combustion heaters in the first and secondembodiments. Herein, however, the explanation of the essential point isgiven in terms of a necessity for simplifying the description. The likecomponents throughout the internal combustion engines A1, A2 having thecombustion heaters are marked with the like reference symbols with anomission of the explanation thereof. Further, the Figures are alsoconfined to the minimum required for the explanation.

Herein, the combustion heater 17 is, as described above, connected inbypass to the main pipe 29 via the air supply passageway 33 and thecombustion gas discharge passageway 35.

The air flow meter is generally defined as an air resisting structurewhich hinders the flow of the air flowing through the intake passageway,and therefore a pressure of the air out of the air flow meter is smallerthan a pressure of the air entering the air flow meter. Namely, the airflow meter produces a difference in the air pressure between the inletand the outlet thereof.

The air flow meter 70 as the intake resistance structure with the airpressure difference produced between the inlet and the outlet thereof,is provided at a portion along the main line with respect to thecombustion heater 17 connected in bypass to the main pipe 29, morespecifically at a portion 29 m of the main pipe 29 between theconnecting point c1 of the air supply passageway 33 to the main pie 29and the connecting point c2 of the combustion gas discharge passageway35 to the main pipe 29. In this case, there might be a large pressuredifference between the connecting points C1 and C2, i.e., between theinlet of the air supply passageway 33 and the outlet of the combustiongas discharge passageway 35, and hence an air flow velocity in thecombustion chamber 17 d of the combustion heater 17 located between theair supply passageway 33 and the combustion gas discharge passageway 35,becomes excessive, with the result that an ignition characteristic mightdecline.

Such being the case, the air flow meter used in the third embodiment isconstructed as, e.g., a hot wire type or a film type air flow metercausing a less pressure difference between the inlet side and the outletside.

The internal combustion engine A3 having the combustion heater in thethird embodiment exhibits the following operation and effect as well asexhibiting the same operations and effects as those of the internalcombustion engines A1, A2 having the combustion heaters.

In the internal combustion engine A3 having the combustion heater, theair flow meter 70 is, as explained above, the how wire type or film typeair flow meter in with the smaller pressure difference between the inletside and the outlet side. Therefore, even when the air flow meter 70 asthe air resisting structure is provided at the portion of the main pipe29 between the connecting points C1 and C2 of the air supply passageway33 and the combustion gas discharge passageway 35 to the main pipe 29,it never happens that the air flow velocity in the combustion heater 17increases due to this construction, and therefore the ignition does notbecome difficult to attain. Further, since only the fresh air quantityof the internal combustion engine excluding the air quantity forcombustion in the combustion heater 17 can be measured, the air/fuelratio in the combustion chamber 17 d of the engine 1 can be accuratelyset, and it is possible to enhance the controllability of the engine 1and reduce the emission.

<Fourth Embodiment>

A fourth embodiment of the present invention will be discussed withreference to FIG. 8.

The internal combustion engine having the combustion heater in thefourth embodiment is designated by the reference symbol A4. A differenceof the internal combustion engine A4 having the combustion heater in thefourth embodiment from the internal combustion engine A3 having thecombustion heater in the third embodiment is only the point that the airflow meter 70 is disposed upstream of the connecting point c1.Therefore, other like components are the marked with the like symbols,and the explanation thereof is omitted.

The internal combustion engine A4 having the combustion heater in thefourth embodiment is, as compared with the internal combustion engine A3having the combustion heater in the third embodiment, constructed suchthat the air flow meter 70 is, as described above, disposed upstream ofthe connecting point c1. Accordingly, the applicable air flow meter mayalso be of such a type that there is a pressure difference between theinlet side and the outlet side. It is because the flow velocity of theair flowing inside the combustion heater 17 connected in bypass to themain pipe 29 becomes substantially constant irrespective of theoperation state of the engine 1 by virtue of where the air flow meter 70is disposed, and the ignition of the combustion heater 17 can be therebymade preferable.

To described it in greater details, the air flow meter 70 as the airintake resisting structure is not provided between the connecting pointc1 serving as an inlet portion from the main pipe to the combustionheater 17 connected in bypass to the main pipe 29 via the air supplypassageway 33 and the combustion gas discharge passageway 35, and theconnecting point c2 serving as an outlet portion from the combustionheater 17 to the main pipe 29. Consequently, substantially the samepressure as the pressure acting on the outlet side of the air flow meter70, might act upon the connecting point c1 and the connecting point c2as well. Hence, the pressure difference between the connecting points c1and c2 is, if any, small enough to be ignorable. Accordingly, in theinterior of the combustion heater 17 connected to the connecting pointc2 via the combustion gas discharge passageway 35 as well as beingconnected to the connecting point c1 via the air supply passageway 33,the flow velocity of the air flowing therethrough, i.e., a ventilationvelocity, is substantially constant without a large change thereof.Therefore, the desirable ignition can be expected because of nodifficulty of the ignition of the combustion heater 17. Hence, there mayalso be adopted the air flow meter of such a type as to produce thepressure difference between the inlet side and the outlet side thereof.

<Fifth Embodiment>

A fifth embodiment of the present invention will be discussed referringto FIGS. 9 and 10.

The internal combustion engine having the combustion heater in the fifthembodiment is designated by the reference symbol A5. A difference of theinternal combustion engine A5 having the combustion heater in the fifthembodiment from the internal combustion engine A1 having the combustionheater in the first embodiment is such a point that the intake manifold21 having an intake air pressure sensor 80 is added to the constructionof the internal combustion engine A1 having the combustion heater, andan intake air pressure detected by the intake air sensor is inputted tothe ECU 46 to make the combustion state of the combustion heater 17 morepreferably controllable.

In the internal combustion engine A5 having the combustion heater in thefifth embodiment also, the same components as those of the internalcombustion engine A1 having the combustion heater in the firstembodiment, are marked with the like symbols with an omission of theexplanation thereof.

An operation control routine of the internal combustion engine A5 havingthe combustion heater will be explained with reference to FIG. 10. Notethat this control routine is also a part of a normal flowchart (notshown) when driving the engine 1, and consists of steps 501-510 whichwill hereinafter be described. Further, a difference from the routineshown in FIG. 3 with respect to the internal combustion engine A1 havingthe combustion heater is an addition of steps needed for the ECU 46 tocontrol more preferably the combustion state of the combustion heater 17on the basis of a detected value by the intake air pressure sensor 80,whereby the output of the combustion heater 17 is controlled moreprecisely.

The routine is hereinafter explained.

The judgements made in S501 and in S502 are substantially the same asthose in S101 and S102 in the first embodiment, and hence theirexplanation is omitted. The description start with S503.

In S503, the intake air pressure sensor 80 detects a intake air pressurePa at the intake manifold 21 disposed downstream of the compressor 15 a.

In S504, it is judged whether the intake air pressure Pa is equal to orhigher a set value or not.

The set value connoted herein implies a intake air pressure capable ofrising the combustion gas mixed intake air temperature enough to causethe thermal damage to the intake system structure. When the intake airis compressed by the compressor 15 a, a degree of rise in thetemperature of the intake air toward the engine body 3 increasescorrespondingly.

If Pa≧the set value, the judgement is affirmative, and the processingadvances to S505. Whereas if not, the judgement is negative, and theprocessing proceeds to S506. The processing advances to S505 in a casewhere the engine 1 is in an operation state of such a tendency as toincrease the temperature of the combustion gas mixed intake air towardthe engine body 3 with a rise in the intake air pressure Pa. Further,the processing proceeds to S506 in a case where the engine 1 is in anoperation state of such a tendency as to decrease the temperature of thecombustion gas mixed intake air toward the engine body 3 with a decreasein the intake air pressure Pa.

The intake air pressure Pa is judged to be high in S504, and thereforethe processing advances to S505, in which case there is performed thecontrol of reducing the output of the combustion heater 17. Further, theintake air pressure Pa is judged to be low in S504, and therefore theprocessing advances to S506, in which case there is performed thecontrol of gaining a more increased output of the combustion heater 17than the control, performed in S505, of the output of the combustionheater 17.

In S505, it is judged whether or not the predicted temperature Tm isequal to or higher than a predetermined value “2” set as a specifiedvalue. The predetermined value “2” given herein implies a combustion gasmixed intake air temperature enough to cause the thermal damage to thestructure of intake system.

If Tm≧the predetermined value “2”, the judgement is affirmative, and theprocessing advances to S507. Whereas if not, the judgement is negative,and the processing proceeds to S508.

In S507, the output of the combustion heater 17 is reduced down to atarget value “4” set as a specified value, and thereafter this routineis ended.

In S508, the output of the combustion heater 17 is increased up to atarget value “3” set as a specified value, and thereafter this routineis ended.

The target value “4” and the target value “3” have a relationship suchas the target value “3”>the target value “4”.

The reason why is that if judged to be affirmative in S505, thepredicted temperature Tm becomes much higher than the presenttemperature unless the output of the combustion heater 17 is decreased,it follows that the temperature gets much larger than the predeterminedvalue “2” of the combustion gas mixed intake air temperature enough tocause the thermal damage to the structure of intake system. Further, ifjudged to be negative in S505, since the present combustion gas mixedintake air temperature is lower than the predetermined value “2” enoughto cause the thermal damage to the structure of intake system even byincreasing the output of the combustion heater 17, it is more desirableto increase the output of the combustion heater 17 in order to speed upthe warm-up and the enhance the performance of the car room heater 9.

On the other hand, it is judged in S506 whether or not the predictedtemperature Tm is equal to or higher than a predetermined value “1”different from the predetermined value “2” relative to S505 which hasbeen set as the specified value. The predetermined value “1” givenherein has the same concept as that of the predetermined value “2” andimplies a combustion gas mixed intake air temperature enough to causethe thermal damage to the structure of intake system, but is set toindicate a higher temperature than the predetermined value “2”. This isbecause a degree of supercharging and a temperature rise in thecompressor are small.

If judged to be negative in S506, the processing advances to S509.Whereas if not, the judgement is affirmative, and the processingproceeds to S510.

In S509, the output of the combustion heater 17 is increased up to thetarget value “1” set as the specified value, and thereafter this routinecomes to an end.

In 506 the output of the combustion heater 17 is decreased down to thetarget value “2” set as the specified value, and thereafter this routineis finished.

The target value “1” and the target value “2” have a relationship suchas the target value “1”>the target value “2”. The reason why is that ifjudged to be negative in S506, the predicted temperature Tm is lowerthan the predetermined value “1”, enough to cause the thermal damage tothe structure of intake system even by increasing the output of thecombustion heater 17 in S509, and therefore it is more desirable toincrease the output of the combustion heater 17 for enhancing theperformance of the car room heater 9 as well as for speeding up thewarm-up. Further, if judged to be affirmative in S506, since it might bea trouble that the predicted combustion gas mixed intake air temperatureis as high as causing the thermal damage to the structure of intakesystem. Therefore, the output of the combustion heater 17 is reduceddown to the target value “2” set as the specified value so as to becomea combustion gas mixed intake air temperature not causing the thermaldamage to the structure of intake system by decreasing the pressure ofthe fuel pump relative to the fuel supply pipe 17 e for supplying thecombustion heater 17 with the fuel for combustion or decreasing therotational speed of the blowing fan 45. If the output of the combustionheater 17 is not decreased aiming at the target value “2”, it followsthat the predicted temperature Tm get much higher than the presenttemperature, with the result that the temperature becomes even largerthan the predetermined value “2” of the combustion gas mixed intake airtemperature enough to cause the thermal damage to the structure ofintake system.

Moreover, the target values “1”, “2”, “3” and “4” have a relationshipsuch as the target value “1”>the target value “2”>the target value“3”>the target value “4”

Thus, the output of the combustion heater 17 is controlled correspondingto the relationship of the target value “1”>the target value “2”>thetarget value “3”>the target value “4”, whereby the output of thecombustion heater 17 can be finely controlled corresponding to both ofthe increase/decrease of the intake air pressure Pa and theincrease/decrease of the predicted temperature Tm.

The internal combustion engine A5 having the combustion heater in thefifth embodiment exhibits the following operation and effect whileenhancing the performance of the car room heater and speeding up thewarm-up by utilizing the combustion heater of the combustion heater 17as in the case of the internal combustion engine A1 having thecombustion heater in the first embodiment.

To be specific, in the internal combustion engine A5 having thecombustion heater, if the intake air pressure Pa is equal to or higherthan the predetermined value, the combustion quantity of the combustionheater 17 is decreased.

When the intake air pressure Pa is high, the temperature of the intakeair rises, and it is therefore required that the intake air temperaturebe preferable by decreasing the combustion quantity of the combustionheater 17, corresponding thereto.

What has been thus done makes it feasible to reduce the burden upon theinter cooler 19 coupled with the supercharger 15.

Further, if the intake air pressure Pa is over the set value, and if thepredicted temperature Tm of the combustion gas mixed intake air is overthe predetermined value, the intake air temperature can be setpreferable by decreasing the combustion quantity of the combustionheater 17. In this case also, the burden upon the inter cooler 19 can bereduced.

<Sixth Embodiment>

A sixth embodiment of the present invention will be discussed referringto FIGS. 11 and 12.

The internal combustion engine having the combustion heater in the sixthembodiment is designated by the reference symbol A6. A difference of theinternal combustion engine A6 having the combustion heater in the sixthembodiment from the internal combustion engine A1 having the combustionheater in the first embodiment is only the operation control routine.

Explained therefore is only the operation control routine of theinternal combustion engine A6 having the combustion heater in the sixthembodiment. Note that the reference symbols used for the terms in thedescription of the operation control routine in the sixth embodiment,are the same as those of the internal combustion engine A1 having thecombustion heater in the first embodiment, and hence FIG. 1 showing thefirst embodiment may be referred to.

The operation control routine in the sixth embodiment is described.

This control routine is also a part of a normal flowchart (not shown)when driving the engine 1, and consists of steps 601-604 which willhereinafter be described.

After starting the engine 1, the processing moves to this routine. It isjudged in S601 whether or not the combustion heater 17 is now in theprocess of operation.

If judged to be affirmative in S601, the processing advances to nextS602. Whereas if judged to be negative, this routine is ended. Thenegative judgement may be, for instance, a case of having no necessityfor speeding up the warm-up of the internal combustion engine byoperating the combustion heater 17 or for warming the interior of thecar room by use of the car room heater 9 because of the outside airtemperature being high.

It is judged in S602 whether or not the rotational speed is equal to orlower than a predetermined value. Note that the predetermined value isthe specified rotational speed as the above-mentioned “target rotationalspeed” set slightly higher than the explained previously “limitrotational speed”.

The reason why the target rotational speed is set higher than the limitrotational speed, is that an allowance of some extent is given becauseit might be a trouble that the thermal damage is exerted on thestructure of intake system upon reaching the rotational speed to thelimit rotational speed.

If judged to be affirmative in S602, the processing proceeds to nextS603. Whereas if judged to be negative in S602, this routine is ended,because if the rotational speed is higher than the target rotationalspeed, this might be ruled out for the sixth embodiment.

In S603, the unillustrated fuel pump of the combustion heater 17 isstopped.

In next S604, the blowing fan 45 of the combustion heater 17 is halted,and thereafter this routine is finished.

As described above, in the internal combustion engine A6 having thecombustion heater, when the rotational speed is under the targetrotational speed, the combustion quantity of the combustion heater 17 isdecreased.

In the internal combustion engine A6 having the combustion heater in thesixth embodiment, when the combustion gas of the combustion heater 17enters the main pipe 29, the fresh air turns out to be the combustiongas mixed intake air a3 toward the engine body 3. The combustion gasmixed intake air a3 is the mixed gas of the high-temperature combustiongas a2 with the cold fresh outside air a1′. Hence, if a quantity of thecombustion gas a2 contained in the combustion gas mixed intake air a3per unit capacity remains the same, and if a quantity of the fresh aira1′ is small, the temperature of the combustion gas mixed intake air a3rises. By contrast, if the quantity of the fresh air a1′ is large, thetemperature of the combustion gas mixed intake air a3 lowers. Then, inthe internal combustion engine A6 having the combustion heater of thepresent invention, when the engine rotates at a speed under the targetrotational speed in a low-rotation region where the quantity of the airsucked in the engine body 3, i.e., the quantity of the fresh air a1′ issmall, the contrivance is to decrease the quantity of the combustion gasa2 of the combustion heater 17. Consequently, the temperature of thecombustion gas mixed intake air a3 decreases. Accordingly, it isfeasible to prevent the thermal damage from being exerted upon thestructure of intake system by the ECU 46 well controlling the ratio ofthe combustion gas a2 to the fresh air a1′.

Further, the quantity of the air sucked in the engine body 3 is small inthe low-rotation region, at which time the combustion heater 17 stopswith a halt of the fuel pump thereof and a halt of the blowing fan 45.Therefore, the fuel supply to the combustion heater 17 is cut off, andit follows that the flames in the combustion heater 17 are produced byonly the residual fuel in the combustion heater 17. Normally, theresidual quantity is small, and consequently a duration of flaming comesto an end in a short time. Hence, an heating value of the combustionheater 17 is remarkably reduced. It can be therefore said that thethermal damage to the structure of intake system can be prevented whenthe engine intake quantity is small.

<Seventh Embodiment>

A seventh embodiment of the present invention will be discussedreferring to FIGS. 13 and 14.

The internal combustion engine having the combustion heater in theseventh embodiment is designated by the reference symbol A7. Differencesof the internal combustion engine A7 having the combustion heater in theseventh embodiment from the internal combustion engine A6 having thecombustion heater in the sixth embodiment are a point that the intakemanifold 21 is provided with a throttle valve and a case of a throttlevalve aperture being small is dealt with as a case of the intakequantity being small, and a point that in this connection the operationcontrol routine differs. Therefore, the explanation is concentrated ononly the different points, and the description of the same components isomitted.

A throttle valve 82 linked to an unillustrated accelerator pedal is, asillustrated in FIG. 13, provided at a portion, located downstream of theinter cooler 19, of the downstream-side connecting pipe 27 in such aform as to be attached to an intake manifold 21.

Next, the operation control routine in the seventh embodiment isexplained referring to FIG. 14.

This control routine is also a part of a normal flowchart (not shown)when driving the engine 1, and consists of steps 701-704 which willhereinafter be described. It is to be noted that steps S701, S703 andS704 excluding S702 are the same as steps S601, S603 and S604 in theinternal combustion engine A6 having the combustion heater in the sixthembodiment, and hence the explanation thereof is omitted.

After starting the engine 1, the processing moves to this routine. Then,the processing proceeds via S701 to S702, wherein it is judged whetheror not the aperture of the throttle valve 82 is under a predeterminedvalue. The predetermine value given herein is a numerical value forindicating a specified throttle valve aperture set somewhat lower thananother specified aperture of the throttle valve 82. The formerspecified throttle valve aperture is hereinafter referred to as a targetthrottle valve aperture. The latter is hereinafter referred to as alimit throttle valve aperture. The limit throttle valve aperture is athrottle valve aperture for ensuring a intake air quantity making thecombustion gas mixed intake air temperature high enough to exert thethermal damage to the structure of intake system if the engine is drivenwith a certain aperture when the throttle valve 82 is opened, and if thecombustion heater 17 continues to operate in this driven state.

The reason why the target throttle valve aperture is set higher than thelimit throttle valve aperture, is that an allowance of some extent isgiven because it might be a trouble-that the thermal damage is exertedon the structure of intake system upon reaching the throttle valveaperture to the limit throttle valve aperture.

If judged to be affirmative in S702, the processing proceeds to nextS673. Whereas if judged to be negative, this routine is ended, becauseif the throttle valve aperture is larger than the target throttle valveaperture, this might be ruled out for the invention.

Thus, in the internal combustion engine A7, when the throttle valve isopened with an aperture smaller than the target throttle valve aperture,the quantity of the combustion gas of the combustion heater 17 isdecreased.

In the internal combustion engine A7 having the combustion heater in theseventh embodiment, when the combustion gas of the combustion heater 17enters the main pipe 29, the fresh air becomes the combustion gas mixedintake air a3 toward the engine body 3. The combustion gas mixed intakeair a3 is the mixed gas of the high-temperature combustion gas a2 withthe cold fresh outside air a1′. Hence, if the quantity of the combustiongas a2 contained in the combustion gas mixed intake air a3 per unitcapacity remains the same, and if the quantity of the fresh air a1′ issmall, the temperature of the combustion gas mixed intake air a3 rises.By contrast, if the quantity of the fresh air a1′ is large, thetemperature of the combustion gas mixed intake air a3 lowers. Then, inthe internal combustion engine A7 having the combustion heater of thepresent invention, when the throttle valve is opened with an apertureunder the target throttle valve aperture in which the quantity of theair, i.e., the fresh air a1′ sucked in the engine body 3 is small, thequantity of the combustion gas a2 of the combustion gas mixed intake aira3 is decreased. With this contrivance, the temperature of thecombustion gas mixed intake air a3 lowers. Accordingly, it is feasibleto prevent the thermal damage from being exerted upon the structure ofintake system by the ECU 46 well controlling the ratio of the combustiongas a2 to the fresh air a1′.

Further, when the aperture of the throttle valve is equal to or lowerthan the target throttle valve aperture, the quantity of the air suckedin the engine body 3 is small, at which time the combustion heater 17stops with the halt of the fuel pump and with the halt of the blowingfan 45. Consequently, the fuel supply to the combustion heater 17 is cutoff, and it follows that the flames in the combustion heater 17 areproduced by only the residual fuel in the combustion heater 17.Normally, the residual quantity is small, and hence a duration offlaming comes to an end in a short time. Hence, the heating value of thecombustion heater 17 is remarkably reduced. It can be therefore saidthat the thermal damage to the structure of intake system can be alsothereby prevented when the engine intake quantity is small.

<Eighth Embodiment>

An eighth embodiment of the present invention will be discussed byreferring to FIGS. 15 and 16.

The internal combustion engine having the combustion heater in theeighth embodiment is designated by the reference symbol A8. Thisinternal combustion engine A8 having the combustion heater in the eighthembodiment is substantially the same with the internal combustion engineA3 having the combustion heater in the third embodiment. The onlydifference is that in the eighth embodiment the quantity of fresh airentering into the air flow meter 70 is detected, and the detectedquantity of fresh air is inputted into the ECU 46 as an output signalgenerated by the air flow meter 70, thereby the ECU 46 can make anoptimal control of the combustion heater 17 according to the outputsignal based on the quantity of fresh air. Therefore, the explanation isconcentrated on only the different points, and the description of thesame components is omitted.

As shown in FIG. 15, the air flow meter 70 disposed between theconnecting points c1 and c2 respectively connecting the air supplypassageway 33 with the main pipe 29 and the combustion gas dischargepassageway 35 with the main pipe 29 is electrically connected with theECU 46. In addition, the ECU 46 is electrically connected to the blowingfan 45 and the fuel pump (not shown), and, consequently, the CPU 47 ofthe combustion heater 17 operates directly or indirectly at leastaccording to the output signal generated by the air flow meter 70,thereby the blowing fan 45 and the fuel pump work for the suitablecombustion state of the combustion heater 17. Practically, the outputvalues of the outside air temperature 32, the combustion gas temperaturesensor 36, the number-of-rotations sensor 59, etc. are also factors fordetermining the combustion state of the combustion heater 17. However,for the sake of simplicity, these components are omitted from FIG. 15.The eighth embodiment may be so designed to also include the throttlevalve 82 of the seventh embodiment.

Next, the operation control routine in the eighth embodiment isexplained by referring to FIG. 16.

This control routine is also a part of a normal flowchart (not shown)when driving the engine 1, and consists of steps S801-S804 which willhereinafter be described. It is to be noted that steps S801, S803 andS804, are the same as steps S601, S603 and S604 in the internalcombustion engine A6 having the combustion heater in the sixthembodiment, and hence the explanation thereof is omitted.

After starting the engine 1, the processing moves to this routine. Then,the processing proceeds via S801 to S802, wherein it is judged whetheror not the quantity of fresh air entering into the air flow meter 70 isequal to or lower than a predetermined value. “The predetermined valueof the quantity of fresh air” is a specified quantity of fresh air setslightly higher than another specified quantity of fresh air. The formerspecified quantity of fresh air is hereinafter referred to as a targetquantity of fresh air. The latter is hereinafter referred to as a limitquantity of fresh air. The limit quantity of fresh air is a quantity offresh air for ensuring an intake air quantity making the combustion gasmixed intake air temperature high enough to exert the thermal damage tothe structure of intake system if the internal combustion engine isdriven with this limit quantity of fresh air, and if the combustionheater continues to operate with the driving of the internal combustionengine. If the quantity of fresh air abruptly reaches the limit freshair quantity, it exerts the thermal damage to the structure of intakesystem, and in order to prevent this, some allowance is given.

If judged to be affirmative in S802, the processing proceeds to the nextS803. Whereas if judged to be negative, this routine is ended, becauseif the quantity of fresh air is larger than the target quantity of freshair, this might be ruled out for the eighth embodiment.

Thus, in the internal combustion engine A8 having the combustion heater,when the quantity of fresh air supplied to the engine 1 through the airflow meter 70 is equal to or lower than the target quantity of freshair, the combustion quantity of the combustion heater 17 is decreased.

In the internal combustion engine A8 having the combustion heater in theeighth embodiment, when the combustion gas of the combustion heater 17enters the main pipe 29, the fresh air becomes the combustion gas mixedintake air a3 toward the engine body 3. The combustion gas mixed intakeair a3 is the mixed gas of the high-temperature combustion gas a2 withthe cold fresh outside air a1′ which passes through the air flow meter70 where the flow rate of fresh outside air a1′ is detected.Accordingly, if the quantity of fresh air a1′ is small, and if thequantity of combustion gas a2 contained in the combustion gas mixedintake air a3 per unit capacity remains the same, the temperature of thecombustion gas mixed intake air a3 rises. By contrast, if the quantityof the fresh air a1′ is large, the temperature of the combustion gasmixed intake air a3 lowers. Then, in the internal combustion engine A8having the combustion heater of the eighth embodiment, when the airsucked into the engine body 3, namely, the quantity of fresh airsupplied into the engine body 3 is equal to or smaller than the targetfresh air quantity, the quantity of combustion gas a2 of the combustionheater 17 is decreased, thereby the temperature of the gas mixed intakeair a3 is lowered. Accordingly, it is feasible to prevent the thermaldamage from being exerted upon the structure of the intake system by theECU 46 well controlling the ratio of the combustion gas a2 to the freshair a1′. Further, when the quantity of fresh air is smaller than thetarget quantity of fresh air, the quantity of the air sucked in theengine body 3 is small, at which time the combustion heater 17 stops itsoperation with the halt of the fuel pump and with the halt of theblowing fan 45. Consequently, the fuel supply to the combustion heater17 is cut off, and it follows that the flames in the combustion heater17 are produced by only the residual fuel in the combustion heater 17.Normally, the residual quantity is small, and hence a duration offlaming comes to an end in a short time. Hence, the heating value of thecombustion heater 17 is remarkably reduced. It can be therefore saidthat the thermal damage to the structure of the intake system can bealso prevented when the engine intake quantity is small.

<Ninth Embodiment>

A ninth embodiment of the present invention will be discussed referringto FIGS. 17 and 18.

The internal combustion engine having the combustion heater in the ninthembodiment is designated by the reference symbol A9. The internalcombustion engine A9 having the combustion heater in the ninthembodiment is an improvement of the internal combustion engine A8 havingthe combustion heater in the eighth embodiment. They differ from oneanother only in the points that in the ninth embodiment an exhaustcooler is provided on the combustion gas discharge passageway 35 of thecombustion heater 17, a so-called EGR system is also provided, and anelectrically-driven cooling water pump is attached to the water conduitW1. Thus, portions relative to the above are also different. Hence, onlythe different points are described, and the description of the samecomponents is omitted if not particularly notified.

As illustrated in FIG. 17, an exhaust cooler 84 is disposed in thecombustion gas discharge passageway 35 of the combustion heater 17 andthis exhaust cooler 84 functions mainly when the engine 1 stops. Theexhaust cooler 84 is formed inside with an unillustrated waterpassageway, and both ends 84 a, 84 b of this water passageway areconnected to the water jacket of the engine body 3 and the water conduitW1, respectively.

The exhaust cooler 84 is contrived to function when the engine 1 stops,and therefore the water conduit W1 is fitted with theelectrically-driven cooling water pump 86, whereby the cooling water forthe exhaust cooler 84 can be circulated even during the halt of theengine 1.

Moreover, the engine body 3 is provided with an EGR system 88 forreturning a part of the exhaust gas to the intake system and introducingthe exhaust gas again into the cylinders. The EGR system 88 includes anexhaust gas re-circulation passageway 90 connected in bypass to theengine body 3 for re-circulating the exhaust gas from an exhaust pipe 42to the downstream-side connecting pipe 27. The exhaust gasre-circulation passageway 90 has an EGR valve 92 for controlling a flowrate of the re-circulated exhaust gas. The EGR valve 92 is electricallyconnected to the ECU 46 and opens when the engine 1 stops.

Next, the operation control routine in the ninth embodiment is explainedreferring to FIG. 18.

This control routine is also a part of a normal flowchart (not shown)when driving the engine 1, and consists of steps 901-903 which willhereinafter be described.

After starting the engine 1, the processing moves to this routine, atwhich time it is judged in S901 whether or not the engine 1 now remainsstopped.

If judged to be affirmative in S901, the processing advances to nextS902. Whereas if judged to be negative, this routine is ended, becauseif the engine is not in the stopped state, this might be ruled out forthe ninth embodiment.

In S902, the output of the combustion heater 17 is decreased.

In next S903, the EGR valve is fully opened, and thereafter this routineis finished.

In the internal combustion engine A9 having the combustion heater in theninth embodiment, when the engine 1. is operated, the combustion gas ofthe combustion heater 17 is introduced into the engine body 3 and istherefore, while being supplied for speeding up the warm-up, re-burnedin the cylinders of the engine 1. The re-burned combustion gas emitsalmost no smokes, in other words, contains no carbon, and hence thedurability of the engine 1 is to be improved.

Further, if the combustion heater 17 operates during the halt of theengine 1, the combustion gas emitted out of the combustion heater 17 isflowed to the exhaust pipe 42 and discharged therefrom into theatmospheric air, which may be said to be sufficiently satisfactory as ameasure against the exhaust gas of the combustion heater 17.Accordingly, since the treatment of the exhaust gas of the combustionheater 17 is sufficient even during the stop of the engine 1, it neverhappens that the combustion heater 17 stops due to an insufficienttreatment of the exhaust gas of the combustion heater 17, and thecombustion heater 17 can be independently operated. The combustion heatof the combustion heater 17 is also utilized for warming the air blownfrom the car room heater 9. Therefore, if the combustion heater 17 ismade to work before getting in the car, the car room heater 17 can beswitched ON beforehand, so that the interior of the car room is warm andcomfortable even at the cold time. Note that a process of previouslyswitching ON and warming up the combustion heater 17 may be termedpre-heating of the combustion heater 17.

Then, when the combustion heater 17 is in a pre-heating state, thecombustion gas emitted from the combustion heater 17 is introduced intothe exhaust pipe 42 via the EGR system. At this time, the combustion gasemitted from the combustion heater 17, to begin with, arrives at the EGRsystem 88 through the intake system. Even at that time, however, sincethe combustion gas out of the combustion heater 17 via the exhaustcooler 84 provided in the combustion gas discharge passageway 35 iscooled off, the intake system is not influenced at all by the thermaldamage.

Further, the EGR system 88 is originally provided, whereby the costs canbe reduced.

As discussed above, according to the present invention, the combustiongas emitted from the combustion heater operating when the internalcombustion engine is in the predetermined operation state, is mixed intothe intake air passageway, whereby the fresh air having flowed so farthrough the intake air passageway becomes the high-temperaturecombustion gas mixed intake air assuming the combustion heat of thecombustion gas. Before the combustion gas mixed intake air enters theinternal combustion engine body, the temperature of the combustion gasmixed intake air is obtained. The combustion state of the combustionheater is controlled based on the thus obtained temperature, andtherefore, if this control is preferably carried out, it is feasible torestrain the excessive rise in the intake system temperature due to thecombustion heat while speeding up the warm-up and enhancing theperformance of the car room heater by utilizing the combustion heat ofthe combustion heater. The thermal damage to the intake system structurecan be thereby prevented.

The many features and advantages of the invention are apparent from thedetailed specification and, thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and changes will readily occur to those skilledin the art, it is not desired to limit the invention to the exactconstruction and operation illustrated and described, and accordinglyall suitable modifications and equivalents may be resorted to, fallingwithin the scope of the invention.

What is claimed is:
 1. An internal combustion engine having a combustionheater, comprising: a combustion heater; engine related elements warmedby heat of a combustion gas emitted by said combustion heater during acombustion to speed up a warm-up of said internal combustion engine andto enhance a performance of a car room heater of a vehicle containingsaid internal combustion engine, wherein the combustion gas of saidcombustion heater is introduced into the intake air passageway of saidinternal combustion engine, and a combustion quantity of said combustionheater is decreased when said internal combustion engine is in apredetermined operation state with a small intake air quantity.
 2. Aninternal combustion engine having a combustion heater according to claim1, wherein the rotational speed is under a predetermined value when inthe predetermined operation state.
 3. An internal combustion enginehaving a combustion heater according to claim 1, wherein an aperture ofa throttle valve is under a predetermined value when in thepredetermined operation state.
 4. An internal combustion engine having acombustion heater according to claim 1, wherein said combustion heateris stopped when in the predetermined operation state.